1. Field of the Invention
This invention relates to time division switching system for exchanging voice, data and so on in a time division manner, and particularly to a time division switching system constructed to combine the control and speech path systems and completely distribute thereby to improve the reliability and economy.
2. Description of the Prior Art
So far, a large-scale, high-speed single processor has been used as a control system for a time division switching system. This single processor, however, needs a large space for its installation because it must be duplicated for purposes of reliability. In addition, when a small number of circuits are used, unused parts and ability become large, and thus the processor is very expensive and provides a poor cost performance.
Recently, with the development of the LSI technology, excellent and inexpensive microprocessors have been produced, and now a multiprocessor formed of a plurality of microprocessors is generally used as the control system of the time division switching system.
In the conventional multiprocessor system, however, for example, the functions of a large-capacity processor were realized simply by a plurality of microprocessors, independently of the speech path system or the number of microprocessors was increased or decreased to meet the capacity of the speech path system using a building block construction.
Thus, in the prior art, since each speech path system is tightly coupled, the microprocessors are also tightly coupled with each other. Thus, even if the multiprocessors are dispersed in function share or load share, the amount of communication between the multiprocessors increases, greatly affecting the throughput (or time needed for the connection) and processing ability. In addition, once trouble occurs, the reliability of the system may be seriously lowered, depending on the mode of the trouble. Furthermore, the memory for the control of the speech path system is generally provided in common to the respective processors, and therefore causes a bottleneck particularly in a large system from the reliability point of view.